Diagram of the relationships between structure factors and anomalous differences. Structure factors corresponding to an acentric reflection with indices (h, k, l) and to its Bijvoet mate with indices (−h, −k, −l) are given. The structure factors for the Bijvoet mate are reflected across the x axis for clarity in presentation. The structure factor for the non-anomalous atoms in the structure is designated as FP. The part of the structure factor originating from the real part of the form factor for the atoms in the anomalous substructure (fo + f′) is shown as FH and the part of this structure factor coming from the imaginary part of the form factor (if′′) is shown as FA.